Physics Club Chills Out with Liquid Nitrogen

On April 10th, the Physics Club had its end of the year barbecue in McKelvy’s spacious and beautiful backyard. Many McKelvy scholars were present for the event. The barbecue took place on the stone surface of the old reflecting pool, which now provides a scenic overlook of the Delaware river. McKelvy was able to provide quite a selection of food, with an ample amount of hot dogs and hamburgers for all in attendance. We fired up our humble charcoal grill and prepared our feast. After the long, cold, and icy winter, being about to finally get outside was a relief for all. As we ate, we reflected on the past year and expressed excitement for the coming summer.

Once all the food had been eaten, I (Colin) performed several demonstrations with liquid nitrogen, graciously provided by the physics department for the event. Liquid nitrogen is a nitrogen from the air cooled to the point that it condenses.  It is constantly boiling at a temperature of 77 Kelvin, or -321 degrees Fahrenheit.  It is commonly used to bring other objects down to this temperature. At such low temperature, materials change in surprising ways. A rubber racquetball, normally quite elastic, will shatter if thrown at a hard surface. Without the molecular motion present at room temperature, the rubber becomes brittle. Another cool demonstration involved pouring the liquid nitrogen into warm, soapy water. Suddenly introduced to a large reservoir of heat, the nitrogen undergoes a rapid phase transiting, turning into a gas. The expanding gas is then trapped by the soap, resulting in a shower of vapor-filled bubbles.

The Physics Club and the McKelvy Scholars appreciated the dramatic demonstration of thermodynamic principles. Although the McKelvy House is traditionally associated with the humanities, the scholars believe that math and science form an important part of a liberal arts education. Knowledge of basic scientific principles allows one to have an awareness the natural occurrences and technological advances happening around them. It additionally allows one to make informed decisions about them. I hope that more such events can be hosted in the future to continue the connection between McKelvy and the natural sciences.